<!doctype html>  
<html>

<body  style='overflow:hidden'>  
<canvas id="can" width="400" height="400" style="background:Black;display: block;margin:20px auto;"></canvas>  

<script>  
var sn = [ 42, 41 ], dz = 43, fx = 1, n, ctx = document.getElementById("can").getContext("2d");  
function draw(t, c) {  
ctx.fillStyle = c;  
ctx.fillRect(t % 20 * 20 + 1, ~~(t / 20) * 20 + 1, 18, 18);  
}  
document.onkeydown = function(e) {  
fx = sn[1] - sn[0] == (n = [ -1, -20, 1, 20 ][(e || event).keyCode - 37] || fx) ? fx : n  
};  
!function() {  
sn.unshift(n = sn[0] + fx);  
if (sn.indexOf(n, 1) > 0 || n<0||n>399 || fx == 1 && n % 20 == 0 || fx == -1 && n % 20 == 19)  
return alert("GAME OVER");  
draw(n, "Lime");  
if (n == dz) {  
while (sn.indexOf(dz = ~~(Math.random() * 400)) >= 0);  
draw(dz, "Yellow");  
} else  
draw(sn.pop(), "Black");  
setTimeout(arguments.callee, 130);  
}();  
</script>
  
</body> 

</html>  